This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-167380, filed Jun. 14, 1999, the entire contents of which are incorporated herein by reference.
The present invention relates to a blower, more particularly to a blower suitable for use in a septic tank of bio-filtration type.
In accordance with a rise in the awareness of environmental issues, more and more septic tanks have come into use. A septic tank is employed for the treatment of sewage, which is a water resource, i.e. one of the environmental resources. The septic tank is made up of: a settling separation tank into which sewage is supplied; a contact aeration tank into which the sewage is supplied after being cleared of the solid components in the settling separation tank; and a sedimentation tank to which the sewage is supplied after being treated with microorganisms in the contact aeration tank. In the sedimentation tank, the coagulated microorganisms (sludge) settle, and the supernatant liquid is disinfected and drawn off.
Inside the contact aeration tank, a contact filter medium is provided. Aerobic microorganisms attached on the surface of the contact filter medium propagate themselves in the presence of aerating air, which is supplied from a blower (air blower) by way of a pipe and an air diffuser. The organic matter included in the sewage is thus decomposed. Since the contact filter medium is contaminated in accordance with this decomposition, it is cleaned regularly or irregularly by supplying blowback air from the blower to the contact filter medium for a predetermined length of time of a day.
In the conventional art, a changeover valve is arranged in the pipe through which the compressed air from the blower flows. The changeover valve is provided for supplying aeration air or blowback air from the blower to the contact aeration tank. The valve is changed over between the aeration position and the blowback position. This type of prior art is disclosed in Jpn. Pat. Appln. KOKAI publication No. 10-196547, for example.
In general, the amount of blowback air supplied into a contact aeration tank per unit time is dependent on the type of that contact aeration tank. Regardless of the type, the amount of blowback air supplied must be controlled in relation to the amount of aeration air supplied during the same unit time. In the prior art, the amount of air supplied is controlled by using such a changeover valve as described above. Hence, the control of the changeover valve is complicated, and the amount of air supplied is hard to control with high accuracy.
An object of the present invention is to provide a blower which has solved the problems described above and which enables easy switching of air supply states. An another object of the invention is to provide a blower which enables the entire apparatus incorporating it to be simple in structure, small in size, and low in manufacturing cost.
To achieve these objects, the present invention provides a blower comprising:
a plurality of compressors;
a common air tank for storing compressed air supplied from the compressors;
a switching device for switching the compressed air taken in from the air tank between a first supply state and a second supply state; and
a controller for controlling operations of the compressors and a switching operation of the switching device, the controller being capable of selecting one operation pattern from among a plurality of operation patterns determined by combinations between the compressors and the switching device.
The switching device of the present invention is a changeover valve having: an intake port from which the compressed air supplied from the air tank is taken in; a first discharge port used in the first supply state; and a second discharge port used in the second supply port. The changeover valve selects one of the first and second discharge ports and discharges the compressed air taken in from the intake port to the selected discharge port.
The controller of the present invention selectively drives the compressors. When the changeover valve is changed over to the second discharge port, the controller selects an operation pattern under which the compressors are driven momentarily in an overlap manner.
The controller of the present invention drives the compressors in parallel. Each time the changeover valve is changed over to the second discharge port, the compressors are alternately stopped in accordance with a period in which the second discharge port is used for air supply. The time when the changeover valve is changed over is shifted from the time when the compressors are selectively stopped.
The present invention also provides a blower comprising:
a compressor;
an air tank for storing compressed air supplied from the compressor;
a changeover valve including an intake port from which the compressed air supplied from the air tank is taken in, a first discharge port, a second discharge port, a valve body movable such that the intake port selectively communicates with one of the first and second discharge ports, a member for urging the valve body to a position where the valve body allows the intake port to communicate with the first discharge port, a back-pressure chamber for producing back pressure which enables the valve body to move, against the urging force of the urging member, to a position where the valve body allows the intake port to communicate with the second discharge port, and a back-pressure intake port from which the back pressure is taken into the back-pressure chamber, the valve body of the changeover valve being moved by the urging force of the member to the position where the valve body enables the intake port to communicate with the first discharge port, and when the back pressure is taken into the back-pressure chamber, the valve body is moved by the back pressure to the position where the valve body enables the intake port to communicate with the second discharge port; and
a valve including an intake port from which the compressed air supplied from the air tank is taken in, the compressed air taken in from the intake port being supplied to the back-pressure intake port of the changeover valve when the changeover valve supplies the compressed air of the air tank to the second discharge port.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.